Congestion-aware topology controls for wireless multi-hop networks

Topology control in ad-hoc networks is the problem of adjusting the transmission power at network nodes in order to achieve the optimal topology that maximizes network performance. Several related works have shown that the optimal throughput per unit energy performance can be achieved when the network topology is minimally connected. A minimally connected topology is achieved when the transmission power used by nodes is the minimum required to keep the network connected. In this paper, we show that in contrast, for typical ad-hoc networks with a few hundred nodes distributed over a few square-miles area, the optimal topology is a function of the load in the network, and is not always the minimally connected topology. We discuss the reason for the phenomenon through both detailed arguments and simulations. We then present three congestion-aware topology control (CATC) algorithms: CATC-CP (CATC-common power), CATC-IP (CATC-independent power), and CATC-MS (CATC-master/slave). The proposed schemes use purely local state to make topology control decisions, but vary in the degree of coordination between nodes once the decisions are taken. The proposed CATC schemes are shown to achieve better performance than that of static topology control schemes using a constant transmission power. (C) 2009 Elsevier B.V. All rights reserved.